1. Field of the Invention
The present invention relates to a storage system and a method of designing a disaster recovery constitution.
2. Description of the Related Art
The storage system comprises at least one storage control device called a ‘disk array system’ or the like, for example and provides a host computer (‘host’ hereinbelow) with data storage services. The storage control device can have a multiplicity of disk drives arranged in an array to construct a RAID (Redundant Array of Independent Disks)-based storage area.
Further, as is known for a so-called disaster recovery system, a backup site can also be provided in a location that is remotely separated from the main site in preparation for a wide scale disaster or the like. The backup site has a backup storage control device installed thereon, and the storage control device stores data groups which are identical to those of the main site.
According to a first conventional technology, a wide-scale disaster or the like can be provided for by remote-copying data from the storage control device of the main site to another storage control device of the backup site (Japanese Application Laid Open No. 2005-215885). Accordingly, even in cases where the main site is stopped by a fault or the like, data processing services can be continued by means of the backup site. However, in cases where a fault occurs at the only backup site prior to recovery of the main site, data processing services cannot be provided for the host.
Therefore, a second conventional technology according to which a plurality of backup sites are provided and system redundancy can be secured even in cases where the main site is suspended has been proposed (Japanese Application Laid Open No. 2005-84953). According to the second conventional technology, a plurality of secondary storage control devices are connected to a primary storage control device as described in paragraph numbers [0008] to [0010]. In cases where the stored content of the primary storage control device is updated, the updated content is immediately transmitted to the first secondary storage control device and reflected in the stored content of the first secondary storage control device. Further, the stored content of the primary storage control device is saved as journal data and the other secondary storage control device suitably reads the journal data and reflects same in its own stored content. Further, the first secondary storage control device creates journal data on the basis of a data update instruction from the primary storage control device and saves the journal data. In cases where the primary storage control device has stopped, the other secondary storage control device reads journal data from the first secondary storage control device and updates its own stored content.
As a third conventional technology, a technology for dynamically selecting a suitable interleaving method on the basis of a variety of main factors of a wireless network is also known (Japanese Application Laid Open No. 2004-72772). However, the third conventional technology is a technology that relates to wireless communications that are unrelated to storage systems.
In the prior art, because a copy of the data is held by two or three sites, the disaster tolerance can be increased. In a case where the number of sites that the user has in their possession is at least two and no more than three, a constitution that increases fault tolerance can be easily designed by connecting the respective sites.
However, in recent years, large-scale storage systems comprising a multiplicity of sites have also been known. In a storage system comprising a multiplicity of sites, because the overall constitution of the system is complicated, it takes effort to construct a suitable disaster recovery constitution that satisfies user expectations. The user selects a plurality of sites from among the multiplicity of sites, establishes connections between the selected sites to implement a disaster recovery constitution, and then starts to put the disaster recovery constitution to use.
However, the performance of the disaster recovery constitution is determined by a combination of a plurality of parameters, such as, for example, the physical distance between the respective sites and the speed of the communication lines connecting the respective sites. Therefore, by considering a plurality of parameters for the multiplicity of sites, the user must design the disaster recovery constitution that is considered most appropriate, and this investigation and design of the disaster recovery constitution take time and effort.